1. Field of the Invention
The invention relates to a digital copier that incorporates automatic copy quality correction and calibration. A correction routine corrects a first component of the copier using a known test original before attempting to correct other components that may be affected by the first component.
2. Description of Related Art
In electronic reprographic printing systems, a document or series of documents comprising at least one print job are successively scanned. Upon scanning of the documents, image signals are obtained and electronically stored. The signals are then read out successively and transferred to a printer for formation of the images on paper. Once a document is scanned, it can be printed any number of times or processed in any number oil ways (e.g., words deleted or added, image magnified or reduced). If a plurality of documents comprise a job that is scanned, the processing or manipulation of the scanned documents can include deletion of one or more documents, reordering of the documents into a desired order, or addition of a previously or subsequently scanned document. The printing or processing can be relatively synchronous with scanning, or asynchronous after scanning.
If asynchronous, a time interval exists between scanning and printing or processing. The system can then accumulate a number of scanned jobs in, the system memory for subsequent processing or printing. The order of the jobs to be printed may be different from the order of the jobs as scanned depending on the priority of the jobs and the desires of the operator for increasing productivity or throughput and decreasing printer or scanner down time.
However, even electronic printing systems need occasional alignment or correction of copier components. Copy quality variation both within a reproduction machine and within a machine population is a major concern. Known methods of correction or calibration require extensive operator interaction or provide inadequate correction.
Over time and through extended use, the various subsystems of a copier, even digital copiers, gradually wear, become contaminated, or out of adjustment. Because so many of the subsystems such as the scanner, printer, and illumination subsystems are interrelated and dependent upon each other, errors or degradation of any of these components affects the operation and quality of the other components, usually propagating the errors. Due to this interrelationship, it is often difficult to determine the root cause of an error or to isolate one subsystem's error from affecting other components.
While numerous approaches to correction and calibration of copier operation are known, these usually require extensive trial and error analysis of components. For example, if a mirror or lens is out of focus, this affects the copy that is printed by the printer subsystem. Additionally, if an exposure level for a color is set incorrectly, it results in the printing of a wrong shade. From looking at the copy, it is difficult to determine whether a scanning component, a printing component or even other components relating to illumination such as a light caused the error.
Many calibration systems rely on an operator to visually compare copies with an original and to initiate a correction routine if any undesired properties are detected on the copies. This requires a trained eye and cannot readily ascertain minimal amounts of differences.
There is a need for a simple, automatic calibration method and system which can easily isolate and test individual components so that subsequent testing does not propagate errors from the tested components to untested components.
There also is a need for a reliable correction and calibration diagnostic system for a digital copier that relies on minimal operator assistance and utilizes the sophistication of digital technology to compare and calibrate various components of the copier.